This invention relates to devices of the voltage-divider type, often referred to as potentiometers in connection with volume controls for audio amplifiers of various kinds, and more particularly to a voltage-divider device which can be controlled by a touch of the finger to provide a selected voltage within a preselected range of voltages.
In the prior art, volume controls have generally included an elongated resistance element having three terminals, one at each end of the resistance element and a third which is adjustable along the resistance element. Thus, if a given voltage difference is established across the resistance element by connecting opposite sides of a voltage source to the terminals at the ends of the resistance element, any desired voltage from that present at one end of the resistance element to that present at the other end of the resistance element may be obtained by proper adjustment of the third terminal along the length of the resistance element.
However, the adjustment of such third terminal according to the prior art required the physical movement of the third terminal along the resistance element usually by rotating a knob and often requiring complicated mechanical linkage between the knob and the third terminal. Furthermore, the electrical contact between the third terminal and the resistance element depended upon frictional contact therebetween. Thus, wearing of the device in use is inherent in such devices tending to result in faulty operation and eventually in failure of the device.
According to this invention a voltage-divider device is provided which does not rely on frictional contact between an adjustable terminal and a resistance element to select the voltage output thereof but which may be operated by a touch of the finger. Since there is no adjustable terminal to provide a visual indication of the setting of the voltage divider device, it is an object of this invention to provide a voltage responsive visual indication means physically associated with the resistance element of the voltage divider device to provide a visual indication of the setting thereof.
Briefly, according to this invention, a voltage-divider device comprising a resistive member having an elongated resistive surface and a conductive member having an elongated conductive surface mounted in close space substantially coextensive relationship with each other and means for selectively establishing galvanic contact between each of a plurality of points along the length of the resistive surface and a point corresponding thereto along the length of the conductive surface by a touch of the finger is provided with an elongated voltage responsive visual indication means physically located along the length of the elongated resistive and conductive surfaces in close spaced substantially coextensive relationship therewith. The elongated voltage responsive visual indication means is adapted to produce a different visual indication in response to each of a plurality of different voltages corresponding to each of the plurality of points along the length of the resistive and conductive surfaces. Terminal means for making electrical connection to opposite ends of the resistive surface and terminal means for making electrical connection to the elongated voltage responsive visual indication means are provided.